v20:
-added camera index parameter that allows you to define which connected camera to use (default is 1)
	-this can only be changed when camera is off
-using updated version of z.jsonio JSON reader/writer

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v19: (now works in Max6)
-added frame buffer parameter that allows you to define how long a blob's label/location is retained after it disappears (when tracking enabled)
	-corresponding updates to z.blobSort.js

-now erasing gl context before banging (wasn't doing this before, but it appears to be necessary for Max6)
-explicitly setting gl.videoplane to @transform_reset 1, rather than via the gl.render object, which doesn't seem to work in Max6